The present invention relates to cathode ray tube (CRT) displays, and more particularly to an apparatus for generating either stroke mode symbols or raster displays on a CRT or flat panel display.
Raster scan CRT displays are one well-known type of display. In a raster display, the beam is driven through a predetermined set of lines according to a particular sweep rate and refresh rate to provide substantially complete beam coverage for a particular area. The beam is turned on or off or its intensity modulated at particular pixels to create a particular image.
Another well known type of CRT display is the stroke mode display. In such a display, the X and Y beam deflection amplifiers are independently driven or controlled so as to draw a particular line or symbol. Thus, the beam is driven along only those paths in which the beam is to be turned on; complete beam coverage of an entire area per frame is not obtained.
In some applications, it is desirable to use the capability of both raster and stroke mode displays. One particular application is that of aircraft cockpit displays. Such displays may be used in one mode wherein raster imagery is used such as the display of radar data, and in another mode wherein stroke mode symbology is displayed. Some military fighter aircraft have used CRT display systems which provide the capability of both raster and stroke modes. These known systems have employed separate raster scan generators and stroke mode generators, and switch select the particular generator as desired. One disadvantage of these displays which employ separate generators is the additional circuitry required to implement such devices, which cannot only be expensive to manufacture, but consume substantial space and electrical power in the aircraft, and add substantially to the weight of the aircraft.
It is therefore an object of this invention to provide a symbol/raster generator for a CRT display which is space, weight and power efficient.
Another object of the invention is to provide a CRT controller which is operable in either a stroke or raster mode to produce either a raster scanned display or stroke mode symbology.